1. Technical Field
The present invention relates to an apparatus and method for inspecting the circuit of a substrate.
2. Description of the Related Art
With the recent development of the electronics industry, the requirement that electronic parts be of high functionality has rapidly increased, and thus inspection methods for the circuit of a substrate, performed when the substrate is manufactured, also require high precision, high speed and low cost. However, methods for inspecting the circuit of a substrate, which are currently being generally used, that is, contact pin probe methods, do not yet satisfy the above requirements.
FIG. 1 is a sectional view showing a conventional apparatus for inspecting the circuit of a substrate using contact pin probes.
Referring to FIG. 1, the apparatus for inspecting the circuit of a substrate 15 using contact pin probes includes two pin probes 11 and 12, a voltage source 13, and an ammeter 14.
The first pin probe 11 comes into contact with one end of an electrode 16, formed on one side of the substrate 15, and functions to transfer current supplied by a voltage source 13 to the electrode 16. The second pin probe 12 comes into contact with the other end of the electrode 16, formed on the other side of the substrate 15, and functions to receive current from the electrode 16 and transfer the current to the ammeter 14.
That is, when the electrode 16 is electrified, the voltage source 13, the first pin probe 11, the electrode 16, the second pin probe 12, and the ammeter 14 are sequentially connected in series, so that a closed circuit is formed and current flows into the closed circuit. Therefore, when current is measured using the ammeter 14, a resistance value can be obtained using Ohm's law (R=V/I). When the electrode 16 is electrified, a resistance of 0Ω must be theoretically measured. However, since conducting wires, forming the pin probes 11 and 12 and the closed circuit, have their own resistances, the resistance is measured as a relatively small value and not 0Ω.
Meanwhile, when the electrode 16 is not electrified, current does not flow, and the resistance becomes infinite (V/0=∞).
Therefore, the apparatus for inspecting the circuit of a substrate using pin probes can determine whether the electrode has been electrified by measuring the resistance value.
However, the conventional apparatus for inspecting the circuit of a substrate is problematic because pin probes must be precisely manufactured to cope with the micro-patterning of a substrate, so that the cost of manufacturing pin probes gradually increases, and thus the entire cost required for inspection also increases.
Further, when defects in which an electrode pad has become slightly unfastened and then the electrode is not electrified are present, the electrode may be electrified due to the pressure of pin probes at the time of inspecting the circuit, and thus the results of an erroneous measurement indicating that the electrode is normal may be obtained.
Furthermore, the conventional apparatus is problematic in that, since pin probes must be brought into contact with both ends of the electrode, respectively, measurement time increases, and in that, since heat is generated by the flow of current during the inspection, the electrode may be broken down.